European Pat. Publication No. 267,880 describes an expander for tubular fabric with a frame to which is secured on both sides, right and left, respectively, at least one roller-arrangement each including one outer guide roller around which the tubular fabric is laid. The roller-arrangement spreads the tubular fabric, whereby a drive roller driven for rotation bears with a frictional contact against the guide roller through the tubular fabric for transporting the tubular fabric. The known apparatus includes at least one support roller which takes up tension applied by the tubular fabric to the guide roller. Due to the fact that the drive roller bears against the outside of the guide roller through the tubular fabric, there is the disadvantage that the tension which is applied by the tubular fabric to the guide roller reduces the friction contact between the guide roller and the drive roller so that in operation frequently the friction contact becomes insufficient for an efficient feed advance of the tubular fabric along the expander. As a result, the guide roller and thus the tubular fabric are no longer driven in a continuous fault-free manner, whereby creasing may result.
In order to avoid the just outlined problems, there are provided support rollers which are in a slanted position and bear against the inside of a beaded profile of the guide roller. However, the support rollers of this type merely aggrevate the problem because the support rollers are also driven by frictional contact so that the bearings of the support rollers are loaded which in turn causes a respective delaying or counteracting force that is effective on the tubular fabric to be transported. As a result, the tubular fabric has a tendency to assume a wavy configuration and to sag or crease.
German Pat. Publication No. 2,823,978 discloses an expander for tubular fabric, wherein the expander comprises on its inside a pair of guide rollers which are driven by a drive roller provided for both guide rollers in common. The drive roller causes the tubular fabric to contact the guide rollers similar to the arrangement of the above mentioned European Patent Publication, namely so that the tubular fabric contacts the outside of the guide rollers. As a result, the problem is again not avoided that in the operation the tension applied by the tubular fabric to the guide rollers has a tendency to diminish or even interrupt the friction and hence the force contact or force transmission between the drive rollers and the guide rollers, so that corrugated configurations of the fabric and sagging cannot be satisfactorily avoided.
European Pat. Publication No. 204,660 discloses an expander equipped with endless transport belts meshing or engaging feed advance rollers in a releasable manner. Further, means are provided for changing the width of the expander while the tubular fabric passes over the expander. The change of the expander width is to be accomplished from the outside without interference by the advancing fabric.